【作者】 杨利平；

【导师】 潘才元；

【作者基本信息】 中国科学技术大学 ， 高分子化学与物理， 2008， 博士

【摘要】 高分子科学和材料科学的迅猛发展对基础的化学合成技术提出了新的要求,例如可控性,高选择性,高效率等。适应这种需求而发展起来的活性自由基聚合及点击反应等引起了国内外高分子化学家及材料化学家的广泛关注。活性自由基聚合反应和点击反应不仅为合成各种特殊结构的聚合物,如嵌段、接枝、星形、环形、超支化聚合物提供了有效的手段,也为各种有机或无机材料的改性提供了宽广的技术平台。灵活运用这些高分子学科的前沿技术来合成新的聚合物、对材料进行改性,以及开发新的材料已经成为高分子科学和材料科学中的一个重要课题。在前人工作的基础上,本论文在高分子合成和材料改性方向上进行了有意义的拓展:结合活性自由基聚合和点击反应等,合成了结构复杂的四杂臂星形共聚物和反转星形嵌段共聚物;应用活性自由基聚合和点击反应等,实现了对碳纳米管的聚合物修饰,赋予碳纳米管以良好的溶解性能和特定的功能。具体研究结果简述如下:1.采用RAFT、ROP和点击反应结合的方法,成功地制备了结构明确,分子量分布窄,分子量可以调节的四杂臂星形共聚物。其合成路线是:首先制备聚苯乙烯大分子RAFT试剂PS-SC（S）SC₁₂H₂₅,然后进行PS-SC（S）SC₁₂H₂₅与不可均聚的对炔丙氧基肉桂酸羟乙酯（HEPPA）的反应,合成的聚苯乙烯大分子带有三种功能性端基:羟基,三硫代碳酸酯以及炔基;继而以这种聚苯乙烯大分子作为引发剂或RAFT试剂,依次通过已内酯的开环聚合,丙烯酸甲酯（MA）的RAFT聚合以及与PEO-N₃的点击反应,最终成功地合成了四杂臂星形共聚物S（PS）（PCL）（PMA）（PEO）。2.使用ATRP,ROP和点击反应结合的方法合成了结构明确的反转星形嵌段共聚物（PCL-PS）₂-core-（PCL-PS）₂。其合成路线是:从含2个烷基溴和两个羟基的非等同官能引发剂BMDB开始,首先进行苯乙烯的ATRP,经过末端溴原子的端基转换形成（N₃-PS）₂-core-（OH）₂后,与（CH≡CCH₂）PCL（OOCCH₃）进行点击反应,制备出（PCL-PS）₂-core-（OH）₂,继而以（PCL-PS）₂-core-（OH）₂为大分子引发剂,引发己内酯的开环聚合得到（PCL-PS）₂-core-（PCL-OH）₂,再将末端羟基转化为ATRP引发基团,引发苯乙烯的ATRP,得到目标产物:反转星形嵌段共聚物（PCL-PS）₂-core-（PCL-PS）₂。反转星形嵌段共聚物的特殊结构影响了PS和PCL链段的相分离以及PCL的结晶行为。3.发现了一种新颖高效的对碳纳米管进行非共价修饰的办法。由于三亚苯与碳纳米管之间强烈的的π—π共轭作用,三亚苯为核的六臂星形聚乳酸能够很方便地通过超声处理接枝到未经任何处理的碳纳米管上。提高聚合物的分子量或者使用极性大的溶剂会降低聚合物的接枝率。详细的研究表明,三亚苯基团很可能是锚固在具有比较完善的层状结构的碳纳米管管壁上,二者之间存在着极强的相互作用力。实验结果证明碳纳米管的内在结构在这种修饰过程中可以保留。4.采用溶胶-凝胶法制备了一种具有多级结构的二氧化硅纳米管。首先以MWNT-Br为ATRP引发剂,在碳纳米管表面进行了DMAEMA的ATRP,得到PDMAEMA接枝的多壁碳纳米管MWNT-g-PDMAEMA;然后以此为模板,在PH=4的水溶液中进行四乙氧基硅的水解-缩聚作用,得到一种碳纳米管-二氧化硅纳米复合材料;继而在550℃下于空气中煅烧除掉MWNT-g-PDMAEMA模板,得到具有多级结构的二氧化硅纳米管。这种纳米管的管壁上分布着很多纳米二氧化硅刷。对这种分级结构二氧化硅纳米管的分析表明,这是一种具有高比表面积,多种孔结构并存的复合材料,有望在催化剂和生物传感器中得到应用。5.发展了一种新颖的使用功能性聚合物修饰碳纳米管的办法。首先合成带有冠醚功能团的ATRP引发剂,引发苯乙烯聚合,得到两端分别带有溴原子和冠醚功能团的聚苯乙烯;在末端溴原子转化为叠氮基团之后,利用点击反应将带有冠醚功能团的聚苯乙烯接枝到碳纳米管表面。所得到的碳纳米管-聚苯乙烯-冠醚复合材料表面具有很多冠醚功能团,有望作为相转移催化剂或金属催化剂载体使用。以冠醚端基聚苯乙烯刷修饰的碳纳米管为模板,在碳纳米管壁上组装出粒径均匀的纳米银粒子。更多还原

【Abstract】 With the development of polymer and material sciences,new requirements for basic synthetic technologies,such as controllabilty,high efficiency,high selectivity etc are presented.According to these requirements,those newly developed techniques, such as controlled free radical polymerization and "click chemistry",have been poured great passion by the scientists.They provided the scientists with powerful methods to synthesize various special-structured polymers as well as various organic & inorganic materials.Smartly application of these techniques in polymer synthesis and material modification is one of the most important topics in the field of chemistry. Based on the researchs of the precursors,this dissertation described several outspread works in the synthesis of topologically structured polymers and the modification of carbon nanotubes.All these facts are the origin and impetus of this thesis.The main results obtained in this thesis are as follows:1.The ABCD 4-miktoarm star polymers based on polystyrene（PS）, poly（ε-caprolactone）（PCL）,poly（methyl acrylate）（PMA） and poly（ethylene oxide）（PEO） were synthesized and characterized successfully.Using the mechanism transformation strategy,PS with three different functional groups, hydroxyl,alkyne and trithiocarbonate,PS-HEPPA-SC（S）SC₁₂H₂₅,was synthesized by the reaction of the trithiocarbonate-terminated PS with 2-hydroxyethyl-3-（4-（prop-2-ynyloxy）phenyl）acrylate（HEPPA） in tetrahydrofuran solution.Subsequently,the ring-opening polymerization（ROP） of CL was carded out in the presence of stannous（Ⅱ） 2-ethylhexanoate and PS-HEPPA-SC（S）SC₁₂H₂₅,and then the PS-HEPPA（PCL）-SC（S）SC₁₂H₂₅ obtained was used in the reversible addition -fragmentation chain transfer（RAFT） polymerization of MA to produce the ABC 3-miktoarm star polymer, S（PS）（PCL）（PMA） carrying an alkyne group.The ABCD 4-miktoarm star polymer,S（PS）（PCL）（PMA）（PEO） was successfully prepared by click reaction of the alkyne group on the HEPPA unit with azide-terminated PEO（PEO-N₃）.2.Well-defined inverse star block copolymer,（PCL-PS）₂-core-（PCL-PS）₂ has been successfully prepared through a combination of ATRP,ROP and "Click chemistry".Different from star block copolymer,core-（PCL-PS）₄ prepared using core-first method,the feasible synthetic strategy of the inverse star （PCL-PS）₂-core-（PCL-PS）₂ is a combination of core-first and ann-first methods. Starting from a heterofunctional initiator BMDB,ATRP of St and following "click" reaction of（N₃-PS）₂-core-（OH）₂ with linear（CH≡CCH₂）PCL -（OOCCH₃） produced block copolymer（PCL-PS）₂-core-（OH）₂.After ROP of CL using（PCL-PS）₂-core-（OH）₂ as macroinitiator and successive transformation of terminal hydroxyl groups into bromine groups,ATRP of St using （PCL-PS）₂-core-（PCL-Br）₂ as macroinitiator yielded successively inverse star block copolymer,（PCL-PS）₂-core-（PCL-PS）₂.The intricate structure of the inverse star block copolymer influenced the microphase separation of PS and PCL segments,in turn,affected the crystallization of PCL.3.Found a new noncovalent method to functionalize the carbon nanotubes with polymer.Well-defined hexa-armed star poly（L-lactic acid）（PLLA） with a triphenylene core has been prepared by ring-opening polymerization of LLA.Due to the strongπ-πinteractions between the triphenylene core and multi-walled carbon nanotubes（MWNTs）,the polymer was conveniently immobilized on the surface of the as-received MWNTs by a simple ultrasonic process while the intrinsic graphitic structure of the pristine MWNTs is retained.Both debundling of MWNT ropes and polymer attachment are achieved in a single step.Increasing the molecular weight of the PLLA arms or using high polarity solvent may decrease the amount of the polymers grafted onto the MWNTs.Detailed research demonstrates that the triphenylene cores were probably strongly anchored on the side walls of the nanotubes where the carbons are in well graphitic configuration.4.The preparation of exquisite hierarchical worm-like silica nanotubes by a simple sol-gel method is presented for the first time,in which poly（2-（dimethylamino）ethyl methacrylate）-grafted multi-wall carbon nanotube （MWNT-g-PDMAEMA） was used as sacrificial template.A possible formation mechanism of this interesting structure has been proposed.And the protonated 2-（dimethylamino） groups of PDMAEMA chains is believed to be responsible for the formation of the exquisite hierarchical structure of the formed nanoparticles. The hierarchical silica nanotubes have characteristic of mesoporous materials, such as large surface area,multiple pore distribution and large pore volume,and would have potential applications as catalyst or biosensors.5.Developed a novel method to functionalize the carbon anotubes with end functioned polymer brushes.Firstly,we synthesized crown ether capped polystyrene by ATRP method using an initiator carrying the crown ether group; after the terminal bromine had been transformed into azide groups,theα-azide,ω-crown ether ended polymer was grafted onto the surfaces of carbon nanotubes by "click chemistry" conveniently.The as prepared CNT-PS-Crown composites were good candidates for phase transfer catalysts,carriers for metal catalysts or separation films.Nano sized silver particles have been synthesized in situ on the surfaces of the CNTs due to the host-guest interactions of siliver and crown ether groups.更多还原